Measurement of Bi2 and Bi4 Electron Impact Fragmentation Using Magnetic Polarization

  • K. P. Ziock
  • W. A. Little


We have measured the fragmentation of Bi2 under electron impact ionization (45 eV) by measuring the relative intensity shift produced by a quadrupole magnet on an electrically neutral beam of atomic bismuth (magnetic moment ~ one Bohr magneton) and Bi2 (magnetic moment zero). The large discrepancy between the theoretically predicted and the observed shifts was ascribed to fragmentation in the ionization process. We obtain a fragmentation as defined by Kohl et al.1 of 2. 02 ±. 35. This is slightly higher than their estimates of 1. 54 ±. 20 and exemplifies the importance of fragmentation processes to cluster mass spectroscopy. The same measurement performed on a beam of Bi3 and Bi4 showed no intensity shift for the bismuth trimer. This result is ambiguous due to the unknown magnetic moment of Bi3. However, assuming a single Bohr magneton moment, to within our statistical accuracy, we could ascribe all of the Bi3 detected (Knudsen source) to fragmentation of Bi4 (the observed peak heights for Bi3 and Bi4 were identical.)


Ionization Cross Section Bohr Magneton Cluster Beam Neutral Beam Neutral Cluster 
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Copyright information

© Plenum Press, New York 1987

Authors and Affiliations

  • K. P. Ziock
    • 1
  • W. A. Little
    • 1
  1. 1.Physics DepartmentStanford UniversityStanfordUSA

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